Messages in this thread | | | Date | Sat, 26 May 2018 16:49:47 +0200 | From | Radim Krčmář <> | Subject | Re: [PATCH v4 5/8] KVM: introduce kvm_make_vcpus_request_mask() API |
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2018-05-16 17:21+0200, Vitaly Kuznetsov: > Hyper-V style PV TLB flush hypercalls inmplementation will use this API. > To avoid memory allocation in CONFIG_CPUMASK_OFFSTACK case add > cpumask_var_t argument. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > -bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req) > +bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req, > + unsigned long *vcpu_bitmap, cpumask_var_t tmp) > { > int i, cpu, me; > - cpumask_var_t cpus; > - bool called; > struct kvm_vcpu *vcpu; > - > - zalloc_cpumask_var(&cpus, GFP_ATOMIC); > + bool called; > > me = get_cpu(); > +
Two optimizations come to mind: First is to use for_each_set_bit instead of kvm_for_each_vcpu to improve the sparse case.
> kvm_for_each_vcpu(i, vcpu, kvm) { > + if (!test_bit(i, vcpu_bitmap))
And the second is to pass vcpu_bitmap = NULL instead of building the bitmap with all VCPUs. Doesn't looks too good in the end, though:
#define kvm_for_each_vcpu_bitmap(idx, vcpup, kvm, bitmap, len) \ for (idx = (bitmap ? find_first_bit(bitmap, len) : 0); \ idx < len && (vcpup = kvm_get_vcpu(kvm, idx)) != NULL; \ bitmap ? find_next_bit(bitmap, len, idx + 1) : idx++)
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